Q3 of 105 Page 146

In an AP :

given a = 7, an = 35 find d and s13

d is the common difference

a is the first term = 7


a13 = 35


a13 = a + (13-1)d


35 = 7 + (12)(d)


28 = 12 d


d =


The sum of the series is Sn = [2a + (n-1) d]


S13 = [2×7 + (13-1) ]


= [42]


= 273


More from this chapter

All 105 →
2

Find the sums given below:

(-5) + (-8) + (-11) +…… + (-230)

 3

In an AP :

given a = 5, d = 3, an = 50 find n and sn

 3

In an AP :

given d = 3, a12 = 37 find a and s12

 3

In an AP :

given S10 = 125, a3 = 15 find d and a10